Pension and Other Postretirement Benefits - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1	$ 1
Interest cost	19	19
Expected return on plan assets	(17)	(18)
Recognized net actuarial (gain) loss	7	8
Net periodic cost (benefit)	10	10
Other postretirement benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Interest cost	1	1
Recognized net actuarial (gain) loss	(2)	(1)
Amortization of prior service benefit	(2)	(2)
Net periodic cost (benefit)	$ (3)	$ (2)